// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// Log format information shared by reader and writer.
// See ../doc/log_format.md for more detail.

#ifndef STORAGE_LEVELDB_DB_LOG_FORMAT_H_
#define STORAGE_LEVELDB_DB_LOG_FORMAT_H_

namespace leveldb {
namespace log {

enum RecordType {
  // Zero is reserved for preallocated files
  kZeroType = 0,

  kFullType = 1,

  // For fragments
  kFirstType = 2,
  kMiddleType = 3,
  kLastType = 4
};
static const int kMaxRecordType = kLastType;

static const int kBlockSize = 32768;

// Header is checksum (4 bytes), length (2 bytes), type (1 byte).
static const int kHeaderSize = 4 + 2 + 1;


/* 需要再研究下 */
//4M 每次读取 vlog 的大小，GC 和 恢复 会用到
//static const int vBlockSize = 4*1024*1024;

// VlogHeader 只包含 length (4 bytes).
static const int vHeaderSize = 4;
// write_batch Header
static const int wHeaderSize = 8 + 4 ;

}  // namespace log
}  // namespace leveldb

#endif  // STORAGE_LEVELDB_DB_LOG_FORMAT_H_